Production of maleic acid



NETE

am ss some in. wEIss, OF NEW YonmN. Y., AND CHARLES R. Downs, or cmrrsrnn; Nnw :mRsnY, assmnons TO THE BARRETT COMPANY, A CORPORATION or new snnsny.

rndnucrion or mature new:

1% Drawing.

To all whom it may concern:

Be it knownthat we, JOHN M. Weiss and Census ,R. Downs citizens of the United States, residing at New York city and Clifiside, New Jersey respectively, in the counties of 1) New York, 2 Bergen, and State ew York, (2) ew'Jersey, have invented certain new and useful Improvements in the Production of Maleic Acid, of which" thefollowing is a specification. i This invention relates to the catalytieoxidation of aromatic hydrocarbons and to the production of products of partial oxidation thereirom.- It relates more particularly to the catalytic oxidation of toluene and the production of maleicacid therefrom, but is not intended to be confined solely to this material. The invention comprises a method of efi'ecting the partial or selective oxidation of an aromatic hydrocarbon that contains at least one benzene ring in such a manner that the benzene ring will be split. In practising this invention, the hydrocarbon is subjected to oxidation b oxygen either alone'or admixed with ot er gases, or by meansof anoxy n containinggas, in the presence of a cata zer.

It as heretofore been matic hydrocarbon such as toluene, for example,- could be oxidized so that the oxygen enters into the side chain to-produce benzaldehyde and benzoic acid. ()ther aro-' m'atic ydrocarbons containing side chains are amenable to oxidation-by which the-side chains are oxidized. It is also known that aromatic h drocarbons such as toluene may be oxidize by combustion, much the'same as other combustible hydrocarbons, with" the "formation of carbon dioxid and water.

carbons containing a benzene rin or nucleus i5 perature, the ringer nucleus may be broken and a selective or partial oxidation thereof be made to take place short of complete oxi dation or combustion with the. consequent formation of products of partial oxidation,

' Boone or more of these products being of the aliphatic or straight chain series.

. The invention will be described in connec:

tion withthe following specific, exam le,

by the excess toluene present during the illustrative thereof, but it is to be un er- Specification of Iietters Patent. Application" filed June 18, 1920. Serial No. 389,827.

known that an arc-- The present invention is based upon the-- discovery that by subjecting certain hydro- Patented May no, 1921.

details of this example, which is given to render the invention clearly understood. A finxture of toluene in the vapor phase and an oxygen containing gas such as air, is

' passed through a container which contains vanadium oxid. The vanadium oxid may be distributed upon pumice or any other suitable catalyst carrier, and should be heated to a temperature of 400 C. or above, and may be as high as 550 C. or higher. It is already known that if toluene is passed into contact with vanadium oxid as a catalyst at a temperature between 200 C. and 400 0., the side chain will be oxidized to produce benzaldehyde and benzoic acid. We have found that the production of maleic acid begins in appreciable amounts when tem erature of the vanadium oxid catalyst is :1 out 400 C. with a diminution in the amount of production of benzaldehyde and benzoic acid, but that when the temperature is raised much above'5 C. thecomplete oxidation of the materials takes place to an objectionable extent with a consequent waste of the hydrocarbon that is being oxidized.

We have found in practising this inventon that the proportions of oxygen'and when other conditions are maintained con toluene canbe varied over wide limits, an

increased proportion of oxygen causing a. correspond ng increase in the oxidlzlng effect stunt. A'convenient proportion with a cata- 1 catalyst mass.

The relatiw proportions of the products I present in the exit gases can be made to vary by varying the conditions of operation. If 3' ff a considerable excess of toluene is used over and above that which is oxidized, some of the toluene Will be converted into benzaldehyde and benzoic acid. respectively, it the temperature is not too'high. and the remaining toluene will pass through the reaction reaction. The nitrogen of the air will have effect, tor example, in case moist air, instead of dry air, is used in the process of the Since water is i above. specific example. always practically formed as a product,

' some steam is present as aconsequence.

The conditions of operation may be widely varied and a variation in one. condition of operation will have an eif-ect' which may he counterbalanced or, partially counterbal anced by varying another condition or '.'con'- ditions of operation.- Ampng'these conditions may be mentioned the temperature and pressure atfwhich the reactionis car- 'ried out; the time of contact of the reactive gases withlthe catalyst; the proportion. of catalyst to the reacting gases; the proportion of toluene to oxygen and diluent gases, etc. It will beunderstood that the oxida- "tion takes place 'more readily 'with some catalysts than-with others, thatit islm'orei .rapid' with higher temperatures, that, it

progresses' ifurther with an increase in the time of contact,etc. However, the specific ,conditions'fabove enumerated have been found to give good results'thou'gh the'invention is not restricted to the particular conditionsenumera'ted,"except that the range .of

temperature should be restricted from about 400 G. to. about 550 'Cffor all conditions of operation which we have tried. The

formation of male'ic acid in the vmanner abovedescribed involves the breaking of'the benzenering or nucleus in a characteristic manner, thatis, thebreaking'of this nucleus or ring-in such a way that there remain four carbon-atoms united to each other in the form of the straight chain or'aliphaticcom-- pound (maleic acid), which represents a and benzoic' acid will usually be formed- ,simultaneously with the formation of maleic acid even at-tem'perature considerably above.

- 400 C. and will be present in the reaction products 1n appreciable quantities. These products can be readily separated from each other, for example, by first condensing the materials after they emerge from the reaction chamber, then leaching with water to remove the maleic acid treating with sodium carbonate to remove benzoic acid, and finally distilling themesidual benzaldehyde and excess toluol. While the invention has been particularly described in connection with the partial or selective oxidation of toluene, it includes the; partial or selective, oxidation of other aromatic hydrocarbons which contain at v least 'one' benzene ring or nucleus with one or .more side chains and substitution products of these hydrocarbons. It is essential in;

this invention that thebenzene ring or nucleus be split so that one ormore products are obtained that belong to the straight chain or aliphatic series of compounds. As examples, napthalene can be oxidized similarlyto give phthalicjanhydrid, naphthaquinone and maleic acid, anthraceneto give xylene, methyl naphthalene, fluorene, ace

product of extended oxidation. We claim: p I

. 1'. The-processof producin maleic acid, ben'zaldehyde, andbenzoic aci which com- 'anthraquinone and maleic acid. Similarly,

pnaphthene, etc, will givemaleic'acid as a g -prisesmxidizing toluene-in the'vapqr phase with an oxygen'containing gas' in-the presence of vanadium oxid as a catalyst at a 7 temperature between 400 and 550 C. '2. The process of producing benzaldehyde,

' sta e of partialfoxidation of the aromatirfv benzoic acid and-maleic acid which comby rocarbon.- It'istobe understood that the compound maleic anhydrid-is included maleic acid. Fumaric acid in the-term seems to beformed tosome extent, and is occ'asidnally found among the products of reaction. I v ,After the products of reaction emerge from the reaction chamber, the. 'm'aleic acid may be separated therefrom in any convenlent way, as, for 'example,'by' dissolving the 'lutely necessary to separate the. be'nzaldehyde or benz oic acid if present,-but these materials maybe-passed together with the unreacted toluene through the reaction chamber, whereupon they become further oxidi'zed'together withmoreof the toluene tofo'roduce additional-maleic acid. 1;

will often be found, however, in the practice of this process'that benzaldehyde prises passing toluene and an oxygen con-' taining gas into contact with vanadium oxid,

s'aidioxid being maintained during the reaction at. a temperature of approximately. 430 C.

Y L I 3. The process of producing benzaldehyde, benzoic' acid and maleic 7 acid which comprises passing toluene and an oxygen con-' taining. gas into contact with -vana'dium oxid, said oxid being maintained at a temperature of approximately 430 0., and separating thebenzaldehyde,,benzoic acid and I maleic acidfrom each other. 1

4. The process which comprises passing toluene .and an oxygen contaming gas into contact. with vanadium oxid at a temperature' between 409 C. and 550 0., andrecovering maleic acid from the productsof reaction. 4

. 5. The process which comprises oxidizing toluene 1n the vapor phase with an oxggen containing gas in the presence of vana oxid as a catalyst at a temperature between 4:00 C. and 550- C., separating maleicacid, 130' benzaldeh de, and benzoic acid from any unchange toluene and returning the toluene for a similar oxidizing treatment.

6. The process of producing maleicacid which comprises passing a hydrocarbon conwhich comprises passing a hydrocarbon containing at least one benzenoid ring or nucleus and a substituent group together with an oxygen containing gas into contact with vanadium oxid as a catalyst at a temperature between 400 C. and 550 C.

8. The process. of producing maleic acid' which comprises passing a hydrocarbon containing a single benzenoid ring or nucleus and a substituent group together with an oxygen containing gas into contact with vanadium oxid as' a catalyst at a temperaturebetween 400 C. and 550 C.

9. The process of producing maleic acid which comprises passing a hydrocarbon containing at least one benzenoid ring or nucleus and a substituent group together with an oxygen containing gas into contact with a catalyst at a temperature between 400 C. and 550 C.

r In testimony whereof we affix our signatures.

JOHN M. WEISS. CHARLES R. DOWNS. 

